1. Field of the Invention
The present invention relates to a navigation system. More particularly, the present invention relates to an apparatus and method for restrictively outputting a warning in a navigation system.
2. Description of the Related Art
In general, movable bodies such as ships, airplanes and cars may be provided with navigation systems. A navigation system receives radio signals which represent, for example, a latitude, a longitude and an altitude, from a plurality of satellites included in a GPS (Global Positioning System), and it calculates a current position of a movable body. Further, such a navigation system displays geographical information including the current position according to map data stored in advance. That is, such a general navigation system provides drivers with various information necessary for driving, by means of information received from the GPS; for instance, it displays on a screen a current speed of movement, a path of movement set by a driver before driving, and an optimum path to a destination.
FIG. 1 is a view showing a construction of a conventional navigation system. Referring to FIG. 1, the navigation system includes a GPS satellite 10, a mobile terminal 30 (for instance, cell phone) communicating with a wireless network 40 and a navigation terminal 20 (for instance, a navigation kit) communicating with the GPS satellite 10 and the mobile terminal 30 in order to provide a driver with current position information and travel information of a movable body. FIG. 1 is an example of a case in which the navigation terminal 20 and the mobile terminal 30 are provided in a car.
The navigation terminal 20 receives the position information of the movable body from the GPS satellite 10 and analyzes the position of the movable body. Further, the navigation terminal 20 transmits the position information to the mobile terminal 30 in order to provide the driver with travel information corresponding to the current position of the movable body.
The mobile terminal 30 functions as an interface between the navigation system and the driver. For instance, when the driver requests current position information and information on an optimum path to a destination by means of the mobile terminal 30, the navigation system provides corresponding information to the driver through a display unit and a speaker of the mobile terminal 30.
Further, when the current position information is transmitted from the navigation terminal 20, the mobile terminal 30 receives travel information corresponding to the current position from an information server 50 connected to the mobile terminal through the wireless network 40.
In general, the information server 50 constructs the travel information in a predetermined data format such as RGI (Route Guidance Information) data, and transmits the constructed data format to the navigation terminal 20 via the mobile terminal 30. The navigation terminal 20 analyzes the data format and provides the driver with the travel information of a corresponding position. In this case, the RGI data 60 is information about a link on which the movable body is currently traveling.
FIG. 2 is a view showing a data format of the RGI data 60 utilized conventionally in a navigation system. Referring to FIG. 2, the RGI data 60 utilized conventionally in a navigation system includes a link number field 61, a travel distance field 62, a road type field 63, a travel information field 64, a warning flag field 65 and a warning data field 66. Each field stores the following information:
The link number field 61 stores an identification number of a link on which the movable body is current traveling, the travel distance field 62 stores an entire travel distance of the link, and the road type field 63 stores road types of the link such as local highway, national highway or express highway. The travel information field 64 stores travel information regarding what is in front of the movable body, such as: a left turn 200 m in front and a sharp curve 300 m in front. Further, the warning flag field 65 stores a representation of whether warning data is included in the link or not, and the warning data field 66 stores warning data information to be provided to a driver, such as: ‘speed regulation’ and ‘be cautious of an icy road’.
The navigation terminal 20 receives the RGI data 60 transmitted from the information server 50 through the mobile terminal 30 and confirms the warning flag field 65 of the RGI data 60. From the result of the confirmation, when the warning data has been included in the corresponding RGI data 60 (i.e. the corresponding link), the navigation terminal 20 outputs a voice warning through the speaker based on the warning data stored in the warning data field 66.
When the warning data has not been included in the corresponding link, the navigation terminal 20 shows general paths using the display unit and the speaker based on the travel information stored in the travel information field 64 of the RGI data 60.
In this case, the navigation terminal 20 may output warning data according to each link by itself. For instance, the navigation terminal 20 stores a digital map, determines the current travel information of the movable body by itself and may output the warning data in accordance with a result obtained by analyzing the map information and the travel information.
However, in a conventional navigation system, when the warning data field 66 of the RGI data 60 has included warning data, or when warning data has been generated according to the map information and the travel information, a stored voice warning has been outputted regardless of a current travel state of the movable body. For instance, in the conventional navigation system, when the warning data field 66 of the RGI data 60 has included speed regulation information, a voice warning such as ‘slow down the speed of a movable body to a predetermined speed’ has been outputted, regardless of the current travel speed of the movable body. In more detail, when the RGI data 60 has included warning data such as ‘regulation travel speed is below 60 km/h’, a voice warning such as ‘slow down the current travel speed of the movable body to below 60 km/h’ has been outputted when the movable body has been in a corresponding region of the road, even if the current travel speed of the movable body is below 60 km/h, in the conventional navigation system. Such a voice warning announcing the speed regulation is not only unnecessary to drivers located at an area in which traffic is bumper to bumper, but also it makes the driver's mind unsettled.
Further, in the conventional navigation system enabling a voice warning to be outputted to a driver in an area having unmanned speed cameras, even if the driver has driven below the regulation speed, the voice warning has been outputted regardless of a current travel state of the movable body. This may cause the driver to jam on the brakes in fright and confusion, so that a rear-end collision accident may occur.
Further, in the prior art, a voice warning limited to a particular weather/season/time such as ‘be cautious of sliding if snowing or raining’ or ‘low gear at night’ has been outputted unconditionally, regardless of current weather/season/time. That is, since the voice warning limited to a particular weather/season/time has been outputted without considering the current weather/season/time, preferable travel information has not been provided to the driver and a travel environment grows worse due to the unnecessary voice warning. That is, since all voice warnings set in advance for a corresponding link have been outputted without considering the travel speed of the movable body and the current weather/season/time, there have been many cases in which various necessary pieces of voice-outputted information such as voice warnings, direction instructions and distances remaining according to road conditions have been overlapped by unnecessary voice warnings. Such overlapped voice information has caused drivers to be confused.